By Neus Ferrando Gilabert BSc, MSc (embryologist).
Last Update: 04/30/2014

GnRH antagonists are used during ovulation induction in cycles of in vitro fertilisation, ICSI, PGD, or assisted hatching.

The administration of this medicine in assisted reproduction cycles presents few disadvantages, since GnRH antagonists were created with the aim of obtaining the same benefits as GnRH analogues, but without their disadvantages. For its part, the disadvantages of GnRH analogues may be counterproductive in assisted reproductive treatments, such as the so-called flare-up effect. Conversely, GnRH antagonists do not cause this flare-up effect, which consists of a mass release of FSH and LH hormones.

There is a great deal of controversy regarding its pregnancy rate. Some studies show a decline if compared to the number of pregnancies achieved after a long protocol of GnRH analogues administration. However, others show an increase in the pregnancy rate if compared to that obtained after the administration of GnRH analogues.

These discrepancies are due to the learning curve, which means that the results in the pregnancy rate are subject to use, management, and knowledge about this drug by the health care team.

Disadvantages of GnRH antagonists

The learning curve is inherent to every drug. The use of GnRH antagonists started in 1999; therefore, there are not enough comparative studies on GnRH antagonists and GnRH analogues. Nonetheless, as time goes on, doctors are gaining an increasing insight into its use and to which type of patients should it be prescribed.

Assisted reproductive clinics with previous experience using GnRH antagonists obtain the same pregnancy rate as using GnRH analogues. Furthermore, some clinics using GnRH antagonists already show higher pregnancy rates.

In conclusion, we might even think that its pregnancy rate is slightly lower (between 3% up to 5% less) than that obtained by means of ovarian stimulation protocols where GnRH analogues are used due to the effect of the antagonists on the endometrium, the Fallopian tubes, the follicle, and the oocyte.

Authors and contributors

 Neus Ferrando Gilabert
BSc, MSc
Bachelor's Degree in Biology from the University of Valencia (UV). Postgraduate Course in Biotechnology of Human Assisted Reproduction from the Miguel Hernández University of Elche (UMH). Experience managing Embryology and Andrology Labs at Centro Médico Manzanera (Logroño, Spain). More information